The wafermap process eliminates the inking of reject dies at the wafer fab by using the map data available from a probe test to position the wafer to exact location of all the good die on the Die Bonder or Tape and Reel.
In all wafers, edge dies are almost always bad and usually marked as bad without testing. In small die wafers (for example 25×25 mils), wafer mapping is difficult due to old equipment capability, the wafer will be inked before processing the wafer in pick and place equipment. Because of high yield wafers, almost all the bad dies are edge dies. With small die wafers having high chips per wafer count (50,000 dies) and if the wafer yield are high then inking on the edge of the wafer is more time consuming and not cost effective. Sometimes it is very difficult to even ink in the center. In order to avoid inking edge dies, blind assembly process is used.
Blind assembly process is a process of assembling dies from inkless wafers without using wafer mapping. Some blind assembly processes exist in some new or old pick and place equipments but not all pick and place equipments. The existing blind assembly process tool is a software tool.
It is highly desirable to provide a new blind assembly process that will eliminate inking in small wafers and will work in any pick and place equipment.
It is further desirable to provide a method that will provide a blind assembly process for three types of wafers. The first is a Type I wafer with no inking indicating a bad die. The second is a Type II wafer with no ink in the edge exclusive zone dies and ink dies (reject dies) in the rest of the wafer. The third type is Type III where all bad dies are already inked.